Catheter assemblies are often used to ablate surface tissue within a heart. The catheter assembly typically includes a handle and a catheter shaft extending from the handle, the catheter shaft having a tip portion. The tip portion typically includes a tip ablation electrode at the distal end and a linear ablation electrode along the tip portion spaced apart from the tip electrode. The linear ablation electrode is typically a series of circular band electrodes, one or more spiral electrodes or one or more braided electrodes. While it is desirable to ablate tissue at the target site, it is not desirable to overheat the tissue, or the blood in the vicinity of a target site, because blood can desiccate causing coagulum.